This invention relates to systems and methods for the purification and recovery of potash. Potash was originally produced by leaching wood ashes and evaporating the solution in an iron pot, thus extracting potassium fertilizer.
Potash is important for agriculture because it improves water retention, yield, nutritional value, texture and disease resistance of food crops. It has wide application in the farming of fruits, vegetables, rice, wheat and other grains, sugar, corn, soybeans and cotton, all of which benefit from the nutrient's quality enhancing properties. Potash-based fertilizers have greatly contributed to economic growth in Africa, Asia and Latin America.
Because potash is a fertilizer for the above-mentioned plants, agricultural plant wastes become a reservoir of potassium from which potash can be recovered by extraction from the residue (ashes) which are left from the burning of such agricultural plant wastes. In particular, the agricultural plant wastes which are burned to ashes and from which potash is extracted preferably are cocoa pod husks, plantain (and banana) peels and cola nut husks. Thus, potash may be recovered by extraction from the residue (ashes) left from the burning of the above preferred agricultural plant wastes.
There are many patents that deal with the purification of potash from solutions of potash. Among them are the following:
U.S. Pat. No. 7,892,298, issued Feb. 22, 2011, to Toagosi Co Ltd for “Method for Producing High Purity Caustic Potash” through crystallization by bringing an aqueous solution of caustic potash into a high temperature zone.
U.S. Pat. No. 7,041,268, issued May 9, 2006, to Council of Scientific and Industrial Research for “Process for Recovery of Sulphate of Potash” from sulphate-rich bittern through the use of lime by fractionation of the bittern to obtain kainite type mixed salts and then reaction with muriate of potash to produce crude sulphate of potash.
U.S. Pat. No. 5,456,362, issued Oct. 10, 1995, to The University of British Columbia for “Flotation Process for the Flotation of Coarse Fraction of Potash Ores” by using a column flotation device in which air bubbles are generated by a sparger that utilizes high intensity shearing.
U.S. Pat. No. 4,787,506, issued Aug. 30, 1988, to Kali and Salz Aktiengesellschaft for “Electrostatic Treatment of Milled Crude Potash Salts Containing Kiesserite” by conditioning sequentially with two conditioning agents and feeding the crude potash salt to an electrostatic free fall separator.
U.S. Pat. No. 4,198,288 issued Apr. 15, 1980 to Celanese Polymer Specialties Company for “Desliming of Potash Ores” by treating pulped potash ore with a polygalactomannan gum flocculant, then with a polyamine collector and then subjecting it to froth flotation.
One technical problem to be solved was that the extraction/purification of potash from crude potash still did not provide pure potash which was substantially free of sodium, chlorides, and heavy metals such as iron chromium and nickel.
This problem was attempted to be solved by the teachings of the above described U.S. Pat. No. 7,892,298, which, while it was said to provide high purity caustic potash, was silent in regard to the purification of potash (potassium carbonate). Hence the problem remains to be solved.